1. Field of the Invention
This invention relates to a carrier having a velourlike, finely fibrous topside, in particular a grain leather having a buffed grain side forming the topside, a split leather having a buffed topside or a synthetic velour material having a topside consisting of microfibers, and provided with a dressing which has a grain texture on its face side, the dressing consisting of a consolidated polymeric dispersion and being produced separately on a substrate having a textured surface corresponding to the grain texture, and being bonded to the carrier via a bonding layer formed from a consolidated, polyurethane-containing polymeric dispersion and having been applied to the topside of the carrier. The term “grain texture” is to be understood as also comprehending a nubucklike configuration of the face side of the dressing.
2. Background of the Invention
Full-grain leathers, so-called aniline leathers, which have merely been dyed, but have no dressing on their grain side, have the desirable property of a particularly high air and water vapor permeability, but the grain side of these leathers is not abrasion-resistant, scratch-resistant, lightfast and impervious to soiling, so that these leathers cannot be used for the interiors of vehicles and for the manufacture of shoes.
It has therefore already been proposed to provide the topside of a leather, more particularly of a grain leather which has been incipiently buffed on its grain side, but also of a split leather, and also of a synthetic velour material, with a dressing having a grain texture in order that the face side thereof may have the requisite properties and a leatherlike appearance.
In an existing process, the dressing is initially produced separately on a silicone-rubber substrate having a textured surface corresponding to the grain texture of the dressing. This dressing is produced by a polymeric dispersion comprising not more than 60% by weight, generally 40% by weight, of solids being initially applied to the textured surface of the substrate by blade coating, spraying, roll application or casting, and being allowed to consolidate by heating. Immediately after application, the wet polymeric dispersion has a smooth surface, but, in the course of consolidation, the film formed by this polymeric dispersion shrinks as a result of the removal of water, and the dispersion sags down into the valleys in the texture on the substrate, and at the tips of the texture a dressing layer which is very thin or in circumstances even noncoherent is formed, in particular when the dressing is to have an attractive, deep grain and therefore the substrate has a corresponding, very highly defined texture.
This disadvantage arises particularly because only a thin layer of dispersion can be applied to the substrate, particularly when it has a highly defined texture, since problems can otherwise occur with the drying in that blistering and tearing of the dressing occurs particularly in the grain valleys of the textured substrate.
A further difficulty with the production of the dressing on a textured substrate is that the generally used polyurethane-containing aqueous polymeric dispersions having a solids content of more than 50% by weight is not commercially available and the low solids content of the dispersions which are commercially available engenders pronounced shrinkage on drying.
When a dressing separately produced by following such a known process is peeled off the silicone-rubber substrate, the side facing the textured surface thereof will form the face side of the dressing, so that the grain valleys of the dressing will only be of very low thickness and therefore predetermined breakage areas arise in the dressing as a result of notching and these predetermined breakage areas can result in visible damage to the dressing particularly when the leather provided with such a dressing is exposed to flexing or stretching. This is generally the case when the leather provided with such a dressing is used for the production of interior trim of motor vehicles and of seat cushions, but also as shoe material.
To avoid this disadvantage, it has hitherto always been necessary to provide, between the dressing and the surface of the leather, at least one layer, generally two or more layers, to compensate. Thus, it has already been proposed that the shrinkage loss of the first application of dispersion be compensated for by providing a thick compensating layer which also serves as bonding layer.
In this layered construction, adhesion problems frequently arise between the individual layers, so that there is at least some detachment of layers.
A significant disadvantage of known dressed leathers, particularly when at least one compensating layer is provided, is that the requisite air and water vapor permeability is nonexistent, since any pores or open cells present in the thin dressing are occluded by the compensating layer. This has a negative effect on the breathability of the dressed leather. Particularly in the case of a leather with a dressing having a coarse grain texture, however, bonding to the leather needs very thick compensating layers which adversely affect the properties of the leather.
U.S. Pat. No. 4,923,732 for instance discloses bonding the dressing to the leather surface via a thick compensating layer.
U.S. Pat. No. 4,751,116 and U.S. Pat. No. 6,177,148 likewise show a leather wherein the dressing is bonded to the leather via multiple layers. One of the bonding layers penetrates into the pores in the dressing and lines them, as a result of which water vapor permeability is greatly reduced and air permeability is practically nonexistent. It has therefore been proposed that the dressed leather be mechanically apertured. However, such mechanically produced apertures weaken the leather and lead to soiling of the surface.
Carriers are also known where their dressing is separately produced by applying a dispersion comprising polyurethane and also a crosslinker to a warm substrate. Application is effected in the known processes by blade coating, casting or by means of roll coating, whereby it is impossible to produce a uniformly thick, filmlike dressing. Nor are such thin films obtainable by means of a known spraying process, since a comparatively large amount have to be applied to produce the grain texture, leading to the formation of films of differing thickness in the grain peaks and grain valleys.